Hydraulic lash adjuster



J. DOLZA HYDRAULIC LASH ADJUSTER Nov. 22, 1955 Filed Aug. 18, 1949 nun S A? Summer dfizz 060/26 I 4: a l Gltorncus United States Patent Ofitice r 2,724,373 Patented Nov. 22, 1955 HYDRAULIC LASH ADJUSTER John Dolza, Fenton, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 18, 1949, Serial No. 110,990

16 Claims. (Cl. 123-90) This invntion relates to hydraulic take-up means or lash adjusters for transmitting linear motion from a driving member such as a valve operating cam of an internal combustion engine to a driven member such as the valve of the engine. More specifically my invention concerns such lash adjusters of the type wherein thrust is transmitted from one to the other of said members by two relatively movable elements, such as a cup-shaped cylinder and piston through the medium of an intermediate body of fluid, there being a valved opening in one of the elements through which fluid may be passed at intervals to enlarge said body and thereby restore the abutting relation of the elements with their respective operating and operated members.

Prior devices of the type above set forth have failed to win general acceptance in the art on account of their being subject to one or more of the following disadvantages: (1) expensive to manufacture or assemble, or both, (2) valve mechanism within the device is sensitive to contamination and wear, (3) operation in general is sensitive to aeration and contamination of the engine lubricating oil where the latter is employed as the fluid.

Accordingly itis the principal object of my invention.

to provide an improved hydraulic lash adjuster featuring a small number of parts of simple and rugged design which can be manufactured and assembled at low cost, and which is practically insensitive under usual operating conditions either to contamination or aeration of the fluid supplied thereto.

A further object is to provide a hydraulic lash adjuster having a valved opening for passage of supply fluid to the pressure chamber, the size of which opening is adapted to increase with continued operation in order to free itself of any foreign matter contained in the hydraulic fluid and which is obstructing the closing of said opening.

Another object is to provide a hydraulic lash adjuster having a supply reservoir for the pressure chamber with baffle means for delaying the admixture of make-up fluid therein with the leakage fluid returning thereto from the pressure chamber, pending the de-aeration of andjdiffusion of foreign matterin the make-up fluid.

Still other objects, features and advantages of my invention will be appreciated from a reading of the following description of two illustrative embodiments thereof, having reference to the drawings, wherein:

Figure 1 is a sectional elevational view showing one form of my lash adjuster installed in an overhead valve type internal combustion engine, with arrangements for overhead feeding of engine lubricating oil to the lash adjuster through the engine rocker arm and push rod associated therewith.

Figure 2 is an enlarged sectional view of' the lash adjuster of Figure 1.

Figure 3 is a view similar to Figure 2, but showing a modified form of my lash adjuster adapted for side feeding of engine lubricating oil thereto. 1

Referring first to Figures 1 :and 2, there is shown a lash adjuster designated generally by the numeral 2 which is slidably supported for reciprocal movement in a bore 3 provided therefor in the engine cylinder casing 4. Opposite ends of the lash adjuster are adapted to abut the surface of a cam 5 on the camshaft 6 and the lower end of the engine push rod 7, respectively. The upper end of the push rod, in turn, abuts one end of the valve rocker 8 whose other end abuts the upper end of the stem of the engine valve 9 which is slidably supported for reciprocal movement in a bore 10 provided therefor in the engine cylinder head 11, there being a spring 12 biasing the valve 9 to closed position as shown. Rotation of the camshaft 6 during engine operation causes the cam 5 thereon to reciprocate the last adjuster 2, carrying with it the engine push rod 7 and oscillating the rocker 8 to effect opening and closing of the vaive 9. Providing the lash adjuster 2 is of proper length the valve spring 12 will serve to return it to return it to the base circle of the cam 5 after each valve lift; and no clearance (lash) will exist between it and the valve while the latter is in closed position, thereby pre venting noise and wear due to hammering of the parts, all in a manner well understood in the art.

As seen in Figure 2, my lash adjuster 2 comprises a cylinder 14 having the general shape of an upright cup, the end wall 15 of which rests directly on the cam 5. In nesting relation within and slidably supported by the cylinder 14 is a cup-shaped piston 16 having a downwardly dished end wall 17 which terminates in a central aperture 18. A shallow relief annulus 19, having a width at least equal to range of movement of the piston, is preferably provided in the cylinder bore as shown. The space 20 between the respective cylinder and piston endwalls 15 and 1'7 constitutes the pressure chamber of my lash adjuster and in operation contains a body of fluid (engine oil), not shown, upon which rests the piston 16. The piston end wall 17 is preferably dished as stated to assist in centering a push rod extension 22 the lower end 24 of which extends into the piston and is adapted to abut the upper surface of this wall adjacent the aperture 18. When in such abutting relation the extension 22 serves dually as a valve means closing the aperture 18 and as a member for transmitting thrust to and from the piston.

Within the pressure chamber 20 and held against the end wall 15 of the cylinder by a coil compression spring 26 is an annular abutment member 28, the lower end of which is provided with an outwardly extending flange 30 forming a seat for the spring and serving to loosely center the member in the cylinder. The upper end of this abutment member has an inturned flange 32 defining an opening 34 into which the lower end of the dished piston end wall 17 may intrude when the piston moves downwardly into its lower limiting position against the inturned flange 32. This abutment member is preferably magnetized to attract and hold any magnetizable particles which may be carried into the pressure chamber 20 with the oil, it being desirous to prevent such particles from remaining suspended in the oil and being carried therewith into the very close clearance space between the cylinder and piston side walls. The spring 26 bears at its upper end against the dished piston end wall 17 and serves to bias the piston upwardly against the push rod extension 22 to effect closing of the piston aperture 18.

Upward movement of the piston in the cylinder is limited by a normally outward expanding snap ring 36 lockably engaging a groove 38 in the cylinder bore, and held between this snap ring and a cap piece 40 is a baffle 44 which serves to divide the space internally of j the cylinder and piston into upper and lower compartments 46 and 48. This baffle 44 has a central opening 50 providing clearance around the push rod extension 22 for oil to pass from the upper compartment 46 to the lower compartment 48 at a sufiicient rate to maintain the lower compartment filled duringengine operation. Oil is supplied to the upper compartment 46 from the engine lubrieating system through the port 51 and the connecting longitudinal passage 52 provided in the push rod extension; these in turn being in communication with the longitudinal passage 54 through the push rod 7, the passages 56 and 58 in the valve rocker 8 and the rocker shaft oil gallery 60 as seen in Figure l. The purpose of the baflle 44 is to detain this supply or make-up oil within the upper compartment 46 pending its de-aeration and the diffusion of any foreign particles therein as received from the engine lubricating system, before permitting it to mix with the oil in the lower compartment 48 from which the pressure chamber is supplied. To assist the baffle in these functions the opening 50 is preferably rimmed by an upwardly extending flange 62, which serves to dam up the oil on the baffle and thereby further delay its admixture with the oil in the lower compartment.

The cap piece 40, in addition to effecting an upper retainer for the bafile 44 and a closure for the upper compartment 46, serves 'both as a bushing for slidably supporting the push rod extension 22 and as an abutment for the lower end of the coil compression spring 64. As shown, this cap piece has a depending outer peripheral portion 66 fitting the bore of the cylinder and an upwardly extending central sleeve portion 68 in which the push rod extension 22 has a free sliding fit. The coil compression spring 64 telescopes over the sleeve portion 68 and has its upper end in abutting relation with the underside of an enlargement or head 70 provided on the upper end of the push rod extension 22, the upper face 72 of which sockets the abutting lower end 73. of the push rod 7.

The form of my lash adjuster shown in Figure 3 differs from that heretofore described only in the means for adapting it for side feeding of the make-up oil from the engine lubricating system and in the structure of the baffle employed. The cylinder 102 of this lash adjuster is provided with a plurality of circumferentially spaced ports 104 passing through its side wall just above thesnap ring 36. Each of these ports is in communication with a circumferential groove or annulus 106 formed in the outer wall surface of the piston, which annulusis of suflicient width to be in continuous communication during reciprocation of the cylinder with one or more passages 108 leading through the engine casing 110 to the bore 112 from the engine lubricating system. The bafile 114 is retained in place between the snap ring 36 and the cap piece 40 as in the case of the previously described baffle 44, but differs therefrom in that the portion 116 which extends radially inward from the bore of the cylinder toward the push rod extension 118 also inclines upwardly at a substantial angle to the longitudinal axis. Also, in order that make-up oil may enter the space above the bafile 114, the outer periphery of the latter is provided with a number of circumferentially spaced upward projections 120 upon the upper ends of which rests the cap piece 40.

The operation of both forms of my lash adjuster is substantially. the same. During the portion of each engine revolution in which the engine valve 9 is in closed position, the upper spring 64 biases the lash adjuster cylinder into contact with the base circle of the earn 5 and the push rod extension into abutment with the push rod, eliminating all lash between the latter and the engine valve, and the lower spring 26 biases the piston upwardly against the lower end of the push rod extension to close the piston aperture 18. Thus, when the cam begins to lift the lash adjuster to effect opening of ,the engine valve 9, the push rod extension is in abutment with the piston, ready to transmit the thrust of the latter to the push rod, and the pressure chamber 20 is full of oil. During the lift, the oil in the pressure chamber transmits the thrust of the cylinder to the piston and the latter rises, forcing the push rod extension and push rod upwardly therewith and causing the rocker to open the engine valve against its spring 12. A relatively small amount of oil leaks around the piston from the pressure chamber and enters the lower compartment 48, causing a slight fore-shortening of the lash adjuster during this lifting stroke.

During the downstroke and subsequent to the reclosing of the engine valve the upper spring 64 forces the cylinder to fully return to the base circle of the cam while maintaining the push rod extension in abutment with the push rod. The piston moves downwardly substantially the full distance with the cylinder at this time due to the vacuum condition then existing in the pressure chamber, resulting in an uncovering of the piston aperture 18 by the lower end 24 of the push rod extension. The lower spring 26 thereupon commences to move the piston upwardly in the cylinder, which action tends to draw oil. from the lower compartment 48 through the aperture 18 and into the pressure chamber in restoration of the quantity which leaked around the piston during the previous lifting stroke. This flow of oil through the aperture 18 continues until the piston regains its abutting relation with the lower end of the push rod extension, ready for the next lifting stroke by the cam.

It should be borne in mind that during the cyclic operation just described each form of my lasher is continuously supplied with oil from the engine lubricating system to make-up for losses resulting from seepage, vaporization, etc. In each case the make-up oil is first delivered to the upper compartment 46 where it is dammed up by the bafile and the entrained air allowed to escape between the push rod extension and the sleeve portion 68 of the cap piece 40, after which the oil may drain down into the lower compartment 48 through the opening as needed. Also, in the event a number of foreign particles from the engine should pass in quick succession into the upper compartment, the baffle acts to prevent their entry as a group into the lower compartment where they might cooperate to block the piston aperture 18. The bafile thus performs the additional function of breaking up or diffusing any such group of particles and slowing down, in effect, the frequency at which they eventually reach the aperture 18. The leakage oil, i. e. that which leaks by the piston during the cam lift, however, is free to enter the lower compartment at all times, unhindered by the bafile.

It will be noted that the push rod extension in its function as a valve means for closing the piston aperture 18 is subjected during each cam lift to the full thrust applied to the push rod in forcing the engine valve 9 to open against its spring 12. Consequently, any foreign particles trapped between the lower end 24 of the push rod extension and its seating surface on the piston end wall 17 tend to be crushed to a size small enough to pass through the aperture 18. Also, should the push rod extension be prevented from closing this aperture by reason of such an obstruction during a particular cam lift, the degree of opening will be increased at the end of the next down stroke as the result of the further leak-down of the piston, allowing such particle to pass through the aperture and the push rod extension to recover its closed position for the next cam lift. Thus it will be appreciated that the valve means employed in the lash adjuster is practically insensitive to fluid contamination.

Further, the annular abutment 28 being magnetized serves to prevent the re-cireulation of steel and other magnetically attracted particles which experience has shown form a substantial proportion of the contaminating matter in engine oil fed lash adjusters. And by reason of the shape of this abutment member, particularly its inturned flange 32 surrounding the opening 34, a large percentage of the carbon and other particles passing thereinto with the oil are retained by it and thus do not'have an opportunity to become lodged between the piston side walls and the bore of the cylinder. The

claims to include such modifications within the purview thereof. For example, while the push rod extensions 22 and 118 of the forms of my invention illustrated in Figures 2 and 3, respectively, are preferably articulated with the engine push rod, the invention is considered to cover a construction wherein the push rod and the push rod extension are made integral with each other, and the term push rod? as used in the claims is intended to cover both the integral and the articulated constructions.

I claim:

1. In combination, a generally cup-shaped cylinder, a generally cup-shaped piston in telescopic nesting rela: tion therein having an end wall dished inwardly of the cylinder, said piston being provided with an aperture in the inner extremity of its dishedend wall adapted to permit fluid to flow from one side of the piston to the piston and cylinder, compression spring means be tween the end walls of said piston and cylinder tending to urge the piston outwardly of the cylinder and into,

abutment with said aperture-closing end of the push rod,

an abutment on the inner wall of the cylinder outwardly I of the piston, said cylinder having a port extending through its side wall, outwardly of said abutment for,

the admission of fluid into the cylinder, an outwardly dished bafliejresting on said abutment and provided with an opening surrounding the pushrod throughwhich fluid passing into the cylinder from said port and, overflowing the margin of said opening may thence flow toward the aperture in the piston, a cappiece for, the cylinder providing a slidable support for the push rod, and compression spring means resting on said cap piece and urging the push rod outwardly of the cylinder. i

2. The combination defined by claim 1, and including an abutment member disposed inwardly from the piston and resiliently held in abutting relation with the end wall of the cylinder by said first named spring means, said member serving to positively limit movement of the piston inwardly of the cylinder and being provided with an opening into which said apertured inner extremity of the piston end wall may intrude while the piston is in abutting relation with said member.

3. The combination defined in claim 1, wherein said baflle is provided with projections spacing said cap piece outwardly of the port in the cylinder.

4. In combination, a generally cup-shaped cylinder, a

generally cup-shaped piston in telescopic nesting relation therein, said piston being provided with an aperture in its end wall adapted to permit fluid to flow from one side of the piston to the other, a push rod having one end adapted to abut the end wall of the piston in closing relation with said aperture and its opposite end extending outwardly of the piston and cylinder, compression spring means between the end walls of said piston and cylinder tending to urge the piston outwardly of the cylinder and into abutment with said aperture-closing end of the push rod, an abutment on the inner wall of the cylinder outwardly of the piston, a baflie resting on said abutment and tea s-t3- connecting its outer end with the interior of the cylinder outwardly of said baflle through which fluid may enter the cylinder and upon overflowing the flanged opening in the baflie pass inwardly of the cylinder toward the aperture in the piston, a bushing disposed in the cylinder outwardly of the battle for slidably supporting the push rod, and compression spring means resting on said bushing and urging the push rod outwardly of the cylinder.

5. The combination defined in claim 4, and including a member for limiting movement of the piston inwardly of the cylinder, said member being resiliently held in abutting relation with the end wall of the cylinder and provided with an opening into which a portion of the piston end wall may intrude while the piston is in abutting relation with said member.

6. In hydraulic take-up means, first and secondmembars, a body of fluid in thrust transmitting relation therebetween, resilient means between said members in parallel thrust transmitting relation with said body, one of said members having an aperture for passage of fluid therethrough to and from said body and a chamber in communication with said aperture on the opposite side thereof from said body, said chamber being open both to the admission of replenishment fluid from a source externally of said members and to the leakage of fluid between said members from said body, a push rod extending through said chamber for transmitting thrust to and from said apertured member and constituting a valve closing said aperture during thrust transmission, and a baflle mounted to the other of said members confining the path of movement of the replenishment fluid into said chambers to a relativelytnarrow section surrounding the push rod.

7. t The combination of an operating member, an operated member, means for transmitting motion from said operating member to said operated member comprising a pair of telescopically associated elements, a body of fluid in thrust transmitting relation between said elements,

, valve means for controlling the passage of fluid to and from said body and having a portion adapted to transmit thrust between one of said elements and the member nearest adjacent thereto when said valve means is in closed position, one of said elements forming a fluid reservoir around said portion from which fluid may pass to and from said body when said valve means is in open position, said reservoir being open at one end both to the admission of replenishment fluid from a source externally of said elements and to leakage of fluid between said elements from said body, and a bafiie in the path of movement of the replenishment fluid into said reservoir, said baflie being secured to one of said members and having an upwardly extending portion loosely surrounding said valve means portion.

8. In hydraulic take-up means, inner and outer telescopically associated members, a body of fluid in thrust transmitting relation therebetween, resilient means between said members in parallel thrust transmitting relation with said body, one of said members having an aperture for passage of fluid to and from said body, said members forming a chamber in communication with said aperture on the opposite side of said apertured member from said body, said chamber being open both to the admission of replenishment fluid from a source externally of said members and to the leakage of fluid between said members from said body, and a baflle within the chamher and carried by the outer of said members for restricting the movement of the replenishment fluid toward said aperture.

9. In hydraulic take-up means, a cup, a piston slidable in the cup and adapted to rest on a body of fluid contained therein, said piston having an aperture for passage of fluid to and from said body, a push rod slidable in the cup for transmitting thrust to and from the piston, said push rod constituting a valve serving to close said aperture when in thrust transmitting relation with the piston, and

7 resilient means supported the cup urging the piston in the valve closing direction with respect to the push rod and urging the push rod in the valve opening direction with respect to the piston.

10. In hydraulic take-up means, a cup, a piston slidable in the cup and adapted to abut a body of fluid contained therein, said piston having an aperture for passage of fluid to and from said body, a push rod for transmitting thrust to and from the piston and constituting a valve closing said aperture when in thrust transmitting relation with the piston, resilient means reacting against the cup and push rod respectively tending to urge the push rod outwardly of the cup, and other resilient means reacting against the cup and piston respectively tending to urge the piston outwardly of the cup.

11. In hydraulic take-up means, the combination of telescoping thrust members,'one of said members being adapted to rest on abody of fluid contained in the other, valve means associated with one of said members for controlling the flow of fluid to and from said body and including a portion exposed outside of said telescoping thrust members so as to receive thrust and transmit it to and from said member associated therewith when said valve means is in valve closed position, and resilient means reacting against the other of said members and urging said valve means toward valve open position and urging said member associated therewith toward valve closed position.

12. In hydraulic take-up means, first and second members, a body of fluid in thrust transmitting relation therebetween, said second member having a passage through which fluid may be passed to and from said body, a third member arranged to concurrently close said passage and transmit thrust to andfrom said second member in series with said first member and body, and resilient means reacting against said first member and urging said second and third members toward and away from passage closed position, respectively.

13. In combination, a generally cup-shaped cylinder, a generally cup-shaped piston in telescopic nesting relation therein, said piston being provided with an aperture in its end wall adapted to permit fluid to flow from one side of the piston to the other, a push rod having one end adapted to abut the end wall of the piston in closing relation with said aperture and its opposite end extending outwardly of the piston and cylinder, compression spring means between the end walls of said piston and cylinder tending to urge the piston outwardly of the cylinder and into abutment with said aperture-closing end of the push rod, an abutment on the inner wall of the cylinder outwardly of the piston, said piston and cylinder forming a chamber open both to the admission of replenishment fluid from a source externally of said members and to the leakage of fluid between said piston and cylinder, a baflie on said abutment dividing said chamber into two longitudinally adjacent compartments, a bushing disposed in the cylinder outwardly of the baflle,

and compression spring means urging the push rod outwardly of the cylinder and clamping the baffle between the bushing and said abutment.

14. In a hydraulic tappet, a cylinder closed at one end, a plunger slidable in said cylinder and having an aperture in the base thereof, a valve stem slidably mounted in the cylinder with one end arranged to seat over said aperture, .a' spring disposed between said valve stem and the cylinder to move the valve stem away from said aperture, and a second spring positioned between said plunger and the closed end of the cylinder to oppose the opening of the aperture by said valve stem.

15. A hydraulic tappet comprising a generally cupshaped cylinder, a piston slidably received therein, the interior portions of the cylinder below and above the piston forming a fluid pressure chamber and a fluid supply reservoir respectively, means for introducing fluid to said reservoir from a source externally of the cylinder, said piston having a one-way valved passage for flow of fluid from the reservoir into the pressure chamber, and a magnet in the pressure chamber for retaining magnetically chamber with the inlet and a second compartment joined with the first compartment only through the plunger orifice and a leakage path between the plunger and housing created by the free sliding fit of the plunger in the housing, a spring urging the plunger to seat the mouth of the orifice against the seating face of the needle valve to close the orifice whereby said needle valve spring will extend the tappet to take up slack while said leakage path permits contraction of the tappet under load, and said needle valve and orifice coacting to trap oil in the second compartment under load and to join the two compartments upon release of the load for replenishing the second compartment with oil lost under load through the leakage path.

References Cited in the file of this patent UNITED STATES PATENTS 1,062,580 Bollee May 27, 1913 2,073,709 Paton Mar. 16, 1937 2,098,115 Voorhics Nov. 2, 1937 2,108,514 Summers l Feb. 15, 1938 2,109,815 Best Mar. 1, 1938 2,109,816 Best Mar. 1, 1938 2,140,826 Bettison Dec. 20, 1938 2 ,160,257 Appel F-- M y 3 19. 9 2,185,991 Voorhies et al. Jan. 2, 1940 

